Portion of a motorcycle frame



FIG. 1 is a left side view of a portion of a motorcycle frame, shown in position of use from the left side of a motorcycle; and,

FIG. 2 is a right side view of the portion of the motorcycle frame shown in FIG. 1.

The broken lines immediately adjacent the shaded areas represent the boundaries of the claimed design, while all other broken lines are for illustrative purposes only and form no part of the claimed design. 

We claim the ornamental design for a portion of a motorcycle frame, as shown and described. 